This study reports the manufacture, microstructure, and tribological behaviour of carbon nanotube reinforced aluminium composites against pure aluminium. The specimens were fabricated using powder metallurgy method. The nanotubes in weight percentages of 0.5, 1.0, 1.5, and 2.0 were homogeneously dispersed and mechanically alloyed using a high energy ball milling. The milled powders were cold compacted and then isothermally sintered in air. The density of all samples was measured using Archimedes method and all had a relative density between 92.22% and 97.74%. Vickers hardness increased with increasing CNT fraction up to 1.5 wt% and then reduced. The microstructures and surfaces were investigated using high resolution scanning electron microscope (SEM). The tribological tests showed that the CNT reinforced composites displayed lower wear rate and friction coefficient compared to the pure aluminium under mild wear conditions. However, for severe wear conditions, the CNT reinforced composites exhibited higher friction coefficient and wear rate compared to the pure aluminium. It was also found that the friction and wear behaviour of CNT reinforced composites is significantly dependent on the applied load and there is a critical load beyond which CNTs could have adverse impact on the wear resistance of aluminium.

CitationSieh, R. et al (2015) 'Process optimisation of non-cyanide Ag-PTFE metal matrix composite electroplating for threaded connections', Transactions of the IMF, 93 (5):232.

Threaded tubular fittings are used in a wide variety of industries for critical applications involving fluid transfer in a pressurised or vacuum system. These fittings are made out of corrosion resistant metals such as stainless steel which are desirable in corrosive operating conditions; however, stainless steel is prone to galling which can cause threads to seize, resulting in loss productivity. To prevent this, threads are electroplated using silver (Ag) coatings which prevent galling and serve as a solid lubricant during the make-up process. The Ag cyanide electroplating process currently used in industry is both hazardous to human health and its wastes are detrimental to the environment. The objective of this work is to evaluate environmentally friendly self-lubricating Ag and Ag-PTFE coatings using a non-cyanide electroplating process against the commercially available cyanide Ag coating through the analysis of torque-angle signatures and the torque-angle slope which characterises the make-up process. Results from the experiments suggest that the non-cyanide Ag-PTFE coating is a potentially viable replacement option. Investigation and analysis of the coating performance have also highlighted potential risks of failure through poor lubrication during the make-up process and suggestions for improving the make-up process. Sensitivity: Internal Key Words:Non-cyanide; silver plating; Ag-PTFE; compression fittings; threaded connections; pulse electroplating; Nomenclature

Abstract:The effects of FC-4 cationic surfactant on electrodeposited Ag-PTFE composite coating using direct or pulsed currents were studied using scanning electron microscope (SEM), energy dispersive X-ray (EDS), optical microscope, and a linear tribometer. FC-4:PTFE in various ratios were added to a non-cyanide succinimide silver complex bath. Direct or pulsed current method was used at a constant current density to enable comparison between both methods. A high incorporation rate of PTFE was successfully achieved, with pulsed current being highly useful in increasing the amount of PTFE in the composite coating. The study of coating wear under sliding showed that a large majority of the electrodeposited coatings still managed to adhere to the substrate, even after 10 wear cycles of sliding tests. Performance improvements were achieved on all the samples with a coefficient of friction (CoF) between 0.06 and 0.12.

No abstract